Hydrosilylation palladium catalysed

In addition, various chiral (p-A -sulfonylaminoalkyl)phosphine ligands were earlier employed by Achiwa et al. for the asymmetric palladium-catalysed hydrosilylations of cyclopentadiene and styrene, affording the corresponding... 

Palladium-catalysed hydrosilylation of reactive alkenes, such as norbornene, with silanes R3SiH, chiral at the silicon atom, has been reported to occur with asymmetric amplification.80... 

Groups 10-12. Proton NMR was used to characterise an intermediate r -allyl coordinated pincer complex in the palladium-catalysed allylation of aldehydes and imines.1155 Low-temperature 111 and 13C NMR spectra, and H NOESY data established the mechanism for palladium-catalysed cyclisation/ hydrosilylation of dimethyl diallyl malonate, via (234, E = C02Me).1156 High-pressure 31P 1H NMR studies on coploymerisation of styrene with CO, catalysed by a Pd( 11)-(/L.V-BINAPHOS) complex, gave evidence for a number of active complex intermediates.1157... 

One of the most common methods for the preparation of enantiomerically enriched organosilanes is by palladium-catalysed asymmetric hydrosilylation of alkenes in the presence of trichlorosilane. This area has been dominated by the use of monodentate phosphorus-based ligands and, in particular, Hayashi s MOP ligand/palladium catalyst combination offers a high level of enantioselectivity. The MOP ligands include MeO-MOP (2.139), H-MOP ligands such as (2.140) ... 

Furthermore, Han and Boudjouk demonstrated that formic acid could be used as a source of hydrogen in the palladium catalysed reduction of olefins [248]. Similarly, hydrazine can also be used although the reaction carried out in absolute ethanol is marginally faster at reflux than when carried out in a laboratory cleaning bath [249]. Platinum-catalysed hydrosilylation reactions are also promoted by ultrasound and high yields of the desired product can be obtained within extremely short periods of time [250]. However, rate increases are typically less than ten-fold. 

The (5)-binaphthol-derived phosphoramidite ligands, namely (55), have been found to allow the palladium-catalysed 1,4-hydrosilylation of cyclohexa-1,3-diene with Cl3SiH to proceed with <87% ee, which is the highest enantioselectivity for this reaction reported to date. The enantioselectivity is dramatically dependent on the dialkylamine moiety of the phosphoramidite ligand. ... 

The palladium-catalysed 1,4-hydrosilylation of cyclohexa-l,3-diene with Cl3SiH in the presence of ligand (55) was discussed in the paragraph on silicon. ... 

Scheme 3.7 Tandem double hydrosilylation reaction catalysed by a combination of platinum catalysis and chiral palladium catalysis followed by oxidation.

A palladium-catalysed hydrosilylation of electron-deficient alkynes RC=CEWG has been developed. The reaction is regio- and stereo-selective, giving rise to the (Ej-configured products RCH=C(SiR 3)EWG. ... 

Kitayama K, Uozumi Y, Hayashi T (1995) Palladium-catalysed asymmetric hydrosilylation of styrenes with a new chiral monodentate phosphine ligand. J Chem Soc Chem Commun 1533-1534... 

Concerning enantioselective processes, Fujihara and Tamura have proved that palladium NPs containing (S)-BINAP (2,2 -bis(diphenylphosphino)-l,l -binaphthyl) as chiral stabiliser, catalyse the hydrosilylation of styrene with trichlorosilane, obtaining (S)-l-phenylethanol as the major isomer (ee = 75%) [42]. In contrast, the palladium complex [Pd(BINAP)(C3H5)]Cl is inactive for the same reaction [43]. 

Hydrosilylation of o-allylstyrene (82) with trichlorosilane in the presence of 0.3mol% of a palladium catalyst bearing triphenylphosphine has been found to produce a mixture of indane (83) and the open-chain products (84) and (85) (Scheme 11). The reaction of styrene with trichlorosilane gave a quantitative yield of 1-phenyl-l-(trichlorosilyl)ethane whereas allylbenzene did not give silylation products under the same reaction conditions. These results show that the hydropalladation process is operative in the hydrosilylation of styrene derivatives with trichlorosilane catalysed by palladium-phosphine complexes." ... 

Non-conjugatively linked 9,9/-dibenzosilole polymers have also been reported [44,45]. In an early paper, a dehydrogenation catalyst, bis(l,5-cyclo-octadiene)palladium, was used in the synthesis of poly(9,9-dibenzosilole) 52 (Scheme 6) [45]. Recently, poly(dibenzosilole-vinylene)s 54 were obtained from the platinum-catalysed hydrosilylation of 9,9-dihydrodibenzosilole 51 with 9,9-diethynyldibenzosilole 53 (Scheme 6) [44]. 

Trimethylsilane in the presence of palladium gives 1,4-dihydro-1-trimethylsilylpyr-idine, together with silylated dimer titanium-catalysed hydrosilylation produces a tetrahydro-derivative cleanly. ... 

The lactone concept also allowed easy access to monodentate phosphine ligands with sterically hindered biaryl axes, which catalysed the asymmetric hydrosilylation of styrenes in the presence of palladium (Scheme 5.49). ... 

Aspects of the rhodium-catalysed hydroformylation of olefins have been reviewed. " Copper(ii) acetate catalyses the highly stereoselective solvolysis of -alkenylpentafluorosilicates to -alkenyl ethers under an atmosphere of air. Since the pentafluorosilicates can be obtained via hydrosilylation of acetylenes, the sequence represents a regio- and stereo-selective transformation of acetylenes into carbonyl precursors in moderate yield. The reaction of vinylmercurials and mercury carboxylates catalysed by palladium(ii) acetate provides a stereospecific route to enol carboxylates, which are valuable precursors of specific enolates. ... 

Asymmetric hydrosilylation of alkenes, catalysed by ferrocenylphosphine-palladium complexes, can be utilized in a synthesis of optically active alcohols from alkenes (Scheme 1). The initial optically active silane adducts are converted to alkyl pentafluorosilicates (1) which are then cleaved oxidatively, with retention of configuration, using peracid (c/. 3,132). Complex (2) was the best of several hydrosilylation catalysts examined using this, alcohols with enantiomeric purities of approx. 50% were obtained from norbornene and styrene as the alkenes. 

---